The lung is a major portal of entry for a variety of environmental, chemical, and microbiological agents. Pulmonary alveolar macrophages are a principal defense mechanism against inhaled particulates, but the role of these cells in the defense against chemicals is not clear. In particular, the fate of chemical carcinogens contained in cigarette smoke inhaled into the lungs of smokers is not known. Alveolar macrophages and cells of bronchial epithelium can metabolize some compounds via microsomal and soluble enzymes. We propose to study the metabolism of polycyclic aromatic hydrocarbons by the cells in humans. These investigations will measure the levels of aryl hydrocarbon hydroxylase (AHH) in alveolar macrophages and bronchial epithelium cells lavaged from normal volunteers, and patients with pulmonary tuberculosis or primary lung cancer. Since the capacity for induction of AHH varies between individuals, we will measure AHH induction in several other tissues (muscle, lung, skin, lymphocytes). By studying the ability of these cells to process carcinogenic hydrocarbons, constitutional differences may be delineated to assist in the identification of subjects at risk from exposure to these carcinogens.